Gasket for alkaline battery and method for manufacturing same

Abstract

The present invention provides a gasket for an alkaline battery which enables such a long lifetime that liquid leakage due to carbides of a polyamide resin raw material does not occur, surface wrinkles are hardly generated because of excellent fluidity during molding, and a thin wall portion serving as an explosion-proof safety valve can be normally ruptured until the lifetime of an alkaline battery expires, and a method for manufacturing the same. The gasket for an alkaline battery is formed by injection molding a resin composition, and has a thin wall portion in part. The resin composition is a polyamide 610 resin composition containing a polyamide 610 resin as a main component and a molding aid such as a release agent and a crystal nucleating agent, the polyamide 610 resin having a viscosity number in a range of 80 ml / g or more and 145 ml / g or less.

Description

TECHNICAL FIELD[0001]The present invention relates to a resin gasket for an alkaline battery used in an alkaline battery and a method for manufacturing the same.BACKGROUND ART[0002]Alkaline batteries are widely used from the past as a disposable power source which can be used while being carried upon using toys, flashlights and other electric and electronic equipment. Alkaline batteries are provided with gaskets for insulating an anode from a cathode. In general, as a gasket, an inexpensive polyamide 66 resin as a raw material which is molded into a desired shape by injection molding method is used (Patent Document 1).[0003]Also, as one of the problems required for alkaline batteries, alkaline batteries are required to have a long lifetime. It is known that it is necessary to prevent a gasket from being deteriorated by a strongly alkaline electrolytic solution in order to realize a long lifetime. For example, a gasket including a polyamide 610 resin or a polyamide 612 resin has been...

AI Technical Summary

Benefits of technology

The present invention provides a gasket for an alkaline battery that is made by injection molding using a specific resin composition. The gasket satisfies long lifetime and mechanical properties required for alkaline batteries without causing liquid leakage due to poor quality of the gaskets. The gasket does not produce carbides and surface wrinkles are hard to generate. The thin wall portion serving as an explosion-proof safety valve can be normally ruptured until the lifetime of the alkaline battery expires, which prolongs the lifetime of the gasket.

Problems solved by technology

Also, as one of the problems required for alkaline batteries, alkaline batteries are required to have a long lifetime.

If the internal pressure of the battery increases due to the generated gas, the battery may rupture.

However, when a polyamide resin composition containing a polyamide resin having a high molecular weight as a main component is used in the process of preparing a gasket through injection molding method, it is poor in fluidity, so that the appearance defect called surface wrinkles occurs in a circumference of the thin wall portion serving as an explosion-proof safety valve.

When the surface wrinkles are generated in the thin wall portion, the explosion-proof safety valve may be operated because of the surface wrinkles, which is one of the causes of shortening the lifetime of a battery.

In particular, a polyamide resin composition composed of a polyamide resin having a high molecular weight cannot resolve the problem of the surface wrinkles unless the melting temperature is raised considerably.

However, if the melting temperature is raised until the surface wrinkles are eliminated, the degradation of the polyamide resin composition is accelerated and generation of carbides becomes noticeable.

When the carbides generated in the gasket manufacturing process remain in the thin wall portion, liquid leakage may occur due to the carbide before an alkaline battery reaches its lifetime.

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